Technical Field
The present invention relates to methods of processing mixtures comprising β-glucans and polysaccharides.
Background
β-glucans are polysaccharides of D-glucose monomers linked by β-glycosidic bonds, which occur naturally in some yeast, fungi, plants and bacteria. β-glucans occur in various forms, such as (1,3)-β-glucan, (1,4)-β-glucan, (1,6)-β-glucan, (1,3;1,6)-β-glucan and (1,3;1,4)-β-glucan. The designations (1,3), (1,4) and (1,6) refer to the type of bond found in the β-glucan, and designate the carbon atoms in the D-glucose monomers between which the β-glycosidic bond is formed. Some, but not all, β-glucans are water-soluble. (1,3;1,4)-β-glucans are generally water soluble, at least at sizes below 2,000,000 Daltons. β-glucans are notably found in cereal grains, for example, wheat, barley, rye, and oat. Oats are a particularly good source of (1,3;1,4)-β-glucan.
Liquid compositions comprising β-glucans have been shown to be useful in a variety of ways, including as a food additive, a nutritional supplement, in pharmaceutical compositions, in healthcare, for hair care, skin care and for use in cosmetics. Particularly with regard to skin care, compositions comprising β-glucan have been shown to reduce erythema, as well as acting as an anti-irritant, and can be used to provide relief from insect bites. β-glucan compositions can also be applied to sooth the skin, providing relief from sunburn. β-glucan compositions are also used as an emollient.
Within oat, β-glucans are found predominantly in the aleurone layer and sub-aleurone layers of the grain. In conventional methods for processing grain, the aleurone layer is generally removed with the bran, whilst the sub-aleurone layers are retained as part of the endosperm. Consequently, conventional methods of processing grain are not suitable for maximising the recovery of β-glucans from oats.
In order to produce a β-glucan composition which is suitable for use in cosmetics and health care, it is desirable to produce a composition which comprises β-glucan without significant contamination with other undesirable components of the grain. Several processes have been tried to achieve this. For example, WO 2004/096862 discloses a method to extract and purify cereal β-glucans from milled bran via the use of alkaline extraction and alcohol precipitation. However, this process suffers from being expensive. Further, consumers increasingly wish to purchase naturally produced products. In many countries, in order for a product to be labelled as natural, certain legal and/or regulatory requirements must be met. These often prescribe processes which may not be used in relation to the production of “natural” products. Alkaline extraction and alcohol precipitation are often cited as proscribed forms of processing for natural products, meaning that where alkaline extraction or alcohol precipitation is used to extract β-glucans from cereal grains, in many countries the resultant β-glucan may not be labelled as “natural”. This means the resultant product is less commercially attractive.
A further problem with extraction methods based on alkaline or alcohol extraction is that there are often residual impurities which result in a β-glucan composition which is prone to hazing. Compositions prone to hazing are undesirable, and potentially unsuitable for a variety of uses, particularly for consumer products such as cosmetics and food. US2014/0066510 discloses a method of producing oat extracts which addresses this, but results in a composition with almost no β-glucan.
Different uses of β-glucan compositions may require or benefit from the provision of β-glucans having an average size in a particular range. A further drawback of the processes referred to above is that these processes do not provide the ability to control the size of the β-glucans in the resultant composition.
Therefore there remains a need for a cost effective means of producing liquid compositions comprising β-glucan suitable for a range of uses.